System and method for sensing tissue characteristics

ABSTRACT

A medical device for treating and analyzing tissue includes a plasma applicator having a housing. The housing includes a substantially tubular shape and defines a lumen therethrough. The lumen is in fluid communication with an ionizable media source configured to supply ionizable media thereto. The applicator also includes one or more electrodes coupled to the housing. The electrodes are adapted to couple to a power source configured to energize the electrodes to ignite the ionizable media to form a plasma plume for treating tissue. The device also includes an effluent-collection attachment coupled to the plasma applicator. The effluent-collection attachment is configured to collect a portion of a plasma effluent.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. patent applicationSer. No. 12/791,100, filed on Jun. 1, 2010, the entire contents of whichare incorporated by reference herein.

BACKGROUND

1. Technical Field

The present disclosure relates to plasma applicators and processes forsurface processing and material removal. More particularly, thedisclosure relates to an apparatus and method for generating anddirecting plasma-generated species in a plasma applicator for removingand analyzing tissue.

2. Background of Related Art

Electrical discharges in dense media, such as liquids and gases at ornear atmospheric pressure, can, under appropriate conditions, result inplasma formation. Plasmas have the unique ability to create largeamounts of chemical species, such as ions, radicals, electrons,excited-state (e.g., metastable) species, molecular fragments, photons,and the like. The plasma species may be generated in a variety ofinternal energy states or external kinetic energy distributions bytailoring plasma electron temperature and electron density. In addition,adjusting spatial, temporal and temperature properties of the plasmacreates specific changes to the material being irradiated by the plasmaspecies and associated photon fluxes. Plasmas are also capable ofgenerating photons including energetic ultraviolet photons that havesufficient energy to initiate photochemical and photocatalytic reactionpaths in biological and other materials that are irradiated by theplasma photons.

SUMMARY

Plasma has broad applicability to provide alternative solutions toindustrial, scientific and medical needs, especially workpiece surfaceprocessing at low temperature. Plasmas may be delivered to a workpiece,thereby affecting multiple changes in the properties of materials uponwhich the plasmas impinge. Plasmas have the unique ability to createlarge fluxes of radiation (e.g., ultraviolet), ions, photons, electronsand other excited-state (e.g., metastable) species which are suitablefor performing material property changes with high spatial, materialselectivity, and temporal control. The plasma may remove a distinctupper layer of a workpiece but have little or no effect on a separateunderlayer of the workpiece or it may be used to selectively remove aparticular tissue from a mixed tissue region or selectively remove atissue with minimal effect to adjacent organs of different tissue type.

The present disclosure provides for systems and methods for removing andanalyzing tissue using plasma and other energy-based devices. Duringapplication of plasma, tissue component molecules are vaporized and forman effluent that may then be collected and analyzed either subsequentlyor in real-time to identify types of tissue. This is particularly usefulin cancer treatment procedures where real-time or rapid determinationbetween malignant and normal tissues is beneficial in determining safetreatment margins.

In one embodiment, laser-induced breakdown spectroscopy (“LIBS”) may beutilized in combination with a laser-based tissue treatment device. LIBSuses a pulsed laser in conjunction with one or more focusing lenses tocreate a spark on the surface of the tissue. The resulting opticalemission produced by the spark is then analyzed by a spectrometersystem. In particular, LIBS excites electrons via a laser, and theelectron decay is then detected in an optical spectrometer. In anotherembodiment, mass spectrometry may be utilized. Prior to analysis, thesample is ionized, for example, via a high voltage electrode, and theions are then accelerated in an electric field to a detector.

In a further embodiment, a plasma-based system may be combined with aspectrometer system to provide for more rapid tissue removal as well asgenerating identifiable molecules in the effluent for analysis. A plasmasystem according to the present disclosure includes a power source andan ionizable media source coupled to plasma applicator that initiatesand maintains a plasma plume. The plasma applicator supplies the plasmaplume to the tissue and includes one or more effluent-collectionattachments for collecting vaporized gas and/or particles released bythe tissue upon application of plasma thereto. The plasma system furtherincludes a spectrometer that evaluates and identifies the constituentsof the tissue and outputs that information to the user. The plasmasystem supplies excited atoms and/or pre-ionized molecules to thespectrometer, eliminating the need for a secondary ionization source inthe spectrometer. The plasma system serves a dual purpose as a treatmentdevice and as an excitation source for supplying ions and molecules to aspectrometer. The information from the spectrometer may be outputted ina variety of formats, e.g., identifying ratio of malignant vs. normaltissue, listing percentages of specific compounds, etc. Based on thedisplayed information, the user can determine progression of the tissueremoval procedure and decide whether adequate treatment margins havebeen reached.

The effluent-collection attachment may be an evacuation tube coupled tothe plasma applicator. The tube includes one or more filters forcatching molecules from the effluent. The filters may be of varioussizes to sort the particles based on their size. The molecules may thenbe evaluated by removing the filters and evaluating the molecules usingany suitable spectroscopy systems such as LIBS, spark-induced breakdownspectroscopy, bio-aerosol mass spectrometry, and the like. In anotherembodiment, the effluent-collection attachment may be a secondary plasmachamber that further breaks down the plasma effluent emanating from thetissue. In addition to monitoring the size and type of particles of theplasma effluent, the system may also monitor for spikes in secondary orother harmonics, which are associated with different types of tissuebeing removed.

In another embodiment, the tissue may be treated with a contrast agentor marker that is delivered into tissue, either locally or systemically.The contrast agent may be any compound that is absorbed at differentrates by the different types of tissue cells (e.g., malignant vs.healthy). More specifically, the contrast agent may be a compound thathas different uptake rates for healthy and malignant tissue. Duringtreatment, the presence of the contrast agent in the plasma effluent maythen be used to identify the presence of any cancerous cells.

According to one embodiment of the present disclosure, a medical devicefor treating and analyzing tissue is disclosed. The device includes aplasma applicator having a housing. The housing includes a substantiallytubular shape and defining a lumen therethrough. The lumen is in fluidcommunication with an ionizable media source configured to supplyionizable media thereto. The applicator also includes one or moreelectrodes adapted to couple to the housing. The electrodes are coupledto a power source that energizes the electrodes to ignite the ionizablemedia to form a plasma plume for treating tissue. The device alsoincludes an effluent-collection attachment coupled to the plasmaapplicator, the effluent-collection attachment configured to collect atleast a portion of a plasma effluent.

A method for treatment and analysis of tissue is also contemplated bythe present disclosure. The method includes the steps of generating andsupplying a plasma plume to the tissue through a plasma applicator toform a plasma effluent and collecting at least a portion of the plasmaeffluent through an effluent-collection attachment. The method alsoincludes the steps of analyzing at least the portion of the plasmaeffluent with a spectrometer to generate plasma plume data andprocessing the plasma plume data to determine at least one of type oftissue and effectiveness of energy delivery to the tissue.

Another method for treatment and analysis of tissue is contemplated bythe present disclosure. The method includes the steps of generating andsupplying a plasma plume to the tissue having malignant and normal cellsthrough a plasma applicator to form a plasma effluent and collecting atleast a portion of the plasma effluent through an effluent-collectionattachment. The method also includes the steps of analyzing at least theportion of the plasma effluent with a spectrometer to generate plasmaplume data, processing the plasma plume data to determine a ratio ofmalignant to normal tissue and outputting the ratio and determiningprogression of malignant tissue based on the ratio and terminatinggeneration and supply of the plasma plume based on the progression.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure and, together with a general description of the disclosuregiven above, and the detailed description of the embodiments givenbelow, serve to explain the principles of the disclosure, wherein:

FIG. 1 is a schematic diagram of a plasma system according to thepresent disclosure;

FIG. 2 is a perspective view of a plasma applicator according to oneembodiment of the present disclosure;

FIG. 3 is a perspective view of a plasma applicator according to anotherembodiment of the present disclosure;

FIG. 4 is a perspective view of a plasma applicator according to anotherembodiment of the present disclosure; and

FIG. 5 is a flow chart of a method according to the present disclosure.

DETAILED DESCRIPTION

Plasmas are generated using electrical energy that is delivered aseither direct current (DC) electricity or alternating current (AC)electricity at frequencies from about 0.1 hertz (Hz) to about 100gigahertz (GHz), including radio frequency (“RF”, from about 0.1 MHz toabout 100 MHz) and microwave (“MW”, from about 0.1 GHz to about 100 GHz)bands, using appropriate generators, electrodes, and antennas. Choice ofexcitation frequency, the workpiece, as well as the electrical circuitthat is used to deliver electrical energy to the circuit affects manyproperties and requirements of the plasma. The performance of the plasmachemical generation, the delivery system and the design of theelectrical excitation circuitry are interrelated, i.e., as the choicesof operating voltage, frequency and current levels (as well as phase)effect the electron temperature and electron density. Further, choicesof electrical excitation and plasma applicator hardware also determinehow a given plasma system responds dynamically to the introduction ofnew ingredients to the host plasma gas or liquid media. Thecorresponding dynamic adjustment of the electrical drive, such asdynamic match networks or adjustments to voltage, current, or excitationfrequency are required to maintain controlled power transfer from theelectrical circuit to the plasma.

Referring initially to FIG. 1, a plasma system 10 is disclosed. Thesystem 10 includes a plasma applicator 12 that is coupled to a powersource 14 and an ionizable media source 16. Power source 14 includes anyrequired components for delivering power or matching impedance to plasmaapplicator 12. More particularly, the power source 14 may be any radiofrequency generator or other suitable power source capable of producingpower to ignite the ionizable media to generate plasma. The plasmaapplicator 12 may be utilized as an electrosurgical pencil forapplication of plasma to tissue and the power source 14 may be anelectrosurgical generator that is adapted to supply the device 12 withelectrical power at a frequency from about 0.1 MHz to about 1,000 MHzand, in another embodiment, from about 1 MHz to about 13.6 MHz. Theplasma may also be ignited by using continuous or pulsed direct current(DC) electrical energy.

Power source 14 includes a signal generator 20 coupled to an amplifier22. The signal generator 20 outputs a plurality of control signals tothe amplifier 22 reflective of the desired waveform. The signalgenerator 20 allows for control of desired waveform parameters (e.g.,frequency, duty cycle, amplitude, etc.). The amplifier 22 outputs thedesired waveform at a frequency from about 0.1 MHz to about 1,000 MHzand in another illustrative embodiment from about 1 MHz to about 13.6MHz. The power source 14 also includes a matching network 24 coupled tothe amplifier 22. The matching network 24 may include one or morereactive and/or capacitive components that are configured to match theimpedance of the load (e.g., plasma plume) to the power source 14 byswitching the components or by frequency tuning.

The system 10 provides a flow of plasma through the device 12 to aworkpiece “W” (e.g., tissue). Plasma feedstocks, which include ionizablemedia (FIG. 2), are supplied by the ionizable media source 16 to theplasma applicator 12. During operation, the ionizable media is providedto the plasma applicator 12 where the plasma feedstocks are ignited toform plasma plume 32 containing ions, radicals, photons from thespecific excited species and metastables that carry internal energy todrive desired chemical reactions in the workpiece “W” or at the surfacethereof.

The ionizable media source 16 provides ionizable feedstock to the plasmaapplicator 12. The ionizable media source 16 may include a storage tankand a pump (not explicitly shown) that is coupled to the plasmaapplicator 12. The ionizable media may be a liquid or a gas such asargon, helium, neon, krypton, xenon, radon, carbon dioxide, nitrogen,hydrogen, oxygen, etc. and their mixtures, and the like, or a liquid.These and other gases may be initially in a liquid form that is gasifiedduring application.

During use, the plasma applicator 12 is used to apply the plasma plume32 to the tissue for coagulating, ablating, or otherwise treatingtissue. When the plasma plume 32 is applied to the workpiece “W” (e.g.,tissue) a plasma effluent 31 is generated that includes variouscompounds, particulates and other species from the treated tissue. Theplasma applicator 12 includes an effluent-collection attachment 50 forcollecting the species from the plasma effluent 31 for analysis.

The system 10 also includes a spectrometer 15 coupled to theeffluent-collection attachment 50 to analyze the species collected fromthe plasma effluent 31. The system 10 may include a negative pressuresource 17 to siphon the species into the effluent-collection attachment50 and/or directly into the spectrometer 15. The negative-pressuresource 17 may be a vacuum pump, fan, circulator, and the like. Thespectrometer 15 may be a so-called optical sensor configured as aso-called “lab-on-chip” type device and may utilize any suitablespectroscopy technique such as laser-induced breakdown spectroscopyspark-induced breakdown spectroscopy, bio-aerosol mass spectrometry, andthe like.

In embodiments, the spectromenter 15 may be a surface attracting sensorsuch as a spins sensor utilizing microelectromechanical technologyinstead of the optical sensors of the “lab-on-chip” type diagonistics.The spectrometer 15 may be coupled to a computing device 19 foranalyzing the results spectroscopy analysis. The computing device 19 mayinclude a variety of inputs and/or outputs for interfacing with thespectrometer 15 as well as any other suitable peripheral devices (e.g.,keyboard, mice, monitors, printers, etc.).

With reference to FIG. 2, the plasma applicator 12 is shown. The plasmaapplicator 12 includes a housing 102, which may be formed from anysuitable dielectric material. The housing 102 may have a substantiallytubular shape defining a lumen 103 therethrough terminating in anopening 105 at a distal end of the housing 102. The plasma applicator 12is coupled to the ionizable media source 16 via tubing 104 therebycoupling the lumen 103 in fluid communication with the ionizable mediasource 16.

The plasma applicator 12 is also coupled to the power source 14 via acable 106. The cable 106 encloses a plurality of leads 108 a and 108 bconnecting one or more electrodes 110 a and 110 b to the power source14. The electrodes 110 a and 110 b may be disposed within the lumen 103,within the housing 102 or on an outer surface thereof to provide forresistive or capacitive coupling with the ionizable media being fedthrough the lumen 103. The electrodes 110 a and 110 b may be formed fromany suitable conductive material and may have a variety of shapes andsizes (e.g., ring, needle, etc.).

The plasma applicator 12 includes controls 111 (e.g., toggle switch)coupled to the power source 14 and the ionizable media source 16. Uponactuation, the controls 111 regulate the flow of ionizable media fromthe ionizable media source 16 and the flow of power from the powersource 14, such that the ionizable media flowing through the lumen 103is ignited therein and is ejected from the opening 105 to form theplasma effluent 31.

FIG. 3 illustrates a plasma analysis device 200 that includes a plasmaapplicator 202 and an effluent-collection attachment 204. The plasmaapplicator 202 may be substantially similar to the plasma applicator 12of FIG. 2. The effluent-collection attachment 204 includes a housing 206which may be formed of any suitable type of heat-resistant material. Thehousing 206 may have a substantially tubular shape defining a lumen 208therethrough. The effluent-collection attachment 204 is removablycoupled to the plasma applicator 202, namely, the outer surface of thehousing 206 is coupled to the outer surface of the housing 102. This maybe accomplished by using rails, clamps, and any other suitablemechanisms.

The housing 206 also includes a proximal opening 210 and a distalopening 212 in communication with the lumen 208. The proximal opening210 is coupled to the negative pressure source 17 via tubing 209. Thetubing 209 may be formed from flexible heat-resistant tubing such aspolytetrafluoroethylene (“PTFE”) and the like. The negative pressuresource 17 provides for a continuous flow of air and the plasma effluent31 through the lumen 208. The negative pressure source 17 is alsocoupled to the spectrometer 15 allowing for passage of the speciesgathered from the plasma effluent 31 to the spectrometer 15.

The effluent-collection attachment 204 also includes a plurality offilters 214 a, 214 b, 214 c. The filters 214 a, 214 b, 214 c are ofdifferent filtration sizes and are arranged in a decreasing order oftheir respective sizes from the distal opening 212 to the proximalopening 210. This arrangements allows for sorting of the particulatesfrom the plasma effluent 31 based on their size. Filtering of theparticles allows for passage only of the particles of the smallest sizeto the spectrometer 15. The spectrometer 15 analyzes the filteredparticles in real-time and provides the results to the computing device19, which then processes the results and outputs the same in a readableformat.

In addition to real-time analysis of filtered particles, thespectrometer 15 may also be used to analyze the particles attached tothe filters 214 a, 214 b, 214 c. The effluent-collection attachment 204may be removed after application of the plasma plume 32 to the tissue tocollect the particles from the filters 214 a, 214 b, 214 c and submitthe samples to analysis at the spectrometer 15.

FIG. 4 illustrates a plasma analysis device 300 that includes a plasmaapplicator 302 and an effluent-collection attachment 304. The plasmaapplicator 302 may be substantially similar to the plasma applicator 12of FIG. 2. The effluent-collection attachment 304 is a secondary plasmaapplicator having a housing 306 which may be formed any suitable type ofheat-resistant material and concentrically disposed about the plasmaapplicator 302. The housing 306 may have a substantially tubular shapedefining a lumen 308 therethrough. The lumen 308 is sufficient to fitabout the plasma applicator 302 and to define a secondary plasma chamber309 between the housing 306 and the housing 102. The housing 306 may besecured to the plasma applicator 302 by a spacer 311.

The housing 306 includes a distal opening 316 and a proximal opening318. The effluent-collection attachment 304 includes an adapter 318coupling the proximal opening 318 to the negative pressure source 17 viatubing 312. The adapter 318 may have a funnel-type shape to couple thehousing 306 to the tubing 312. In addition, the adapter 318 may coupleto a plurality tubing connections.

The spacer 311 is disposed between the inner surface of the housing 306and the outer surface of the housing 102. The spacer 311 may be disposedat any point between the housings 102 and 306 to provide for a coaxialconfiguration. The spacer 311 includes a central opening 314 adapted forinsertion of the housing 102 therethrough and one or more flow openings316 disposed radially around the central opening 314 to allow for theflow of plasma effluent 31 and plasma plume 32 to flow through thesecondary plasma chamber 309 as discussed in more detail below. Thespacer 311 may be frictionally-fitted to the housings 102 and 306 tosecure the housing 306 to the housing 102. In one illustrativeembodiment, the spacer 311 may be formed from a dielectric material,such as ceramic, to enhance capacitive coupling between the housings 102and 306.

The housing 102 includes a plurality of openings 150 defined therein tocouple the lumen 103 (e.g., primary plasma chamber) with the secondaryplasma chamber 309. The openings 150 are disposed distally of theelectrodes 110 a and 110 b. This configuration allows the plasma plume32 that is generated within the lumen 103 to enter the secondary plasmachamber 309 and remain therein. In other words, the distally-directedflow of the plasma plume 32 through the opening 105 is counteracted bythe negative pressure source 17, which pulls the plasma effluent 31through the openings 150 and into the secondary plasma chamber 309. Inaddition, the negative pressure source 17 also pulls out the plasmaplume 32 into the secondary plasma chamber 309 through the distalopening 316.

The negative pressure source 17 provides for a continuous flow of airand the plasma effluent 31 through the secondary plasma chamber 309. Thenegative pressure source 17 is also coupled to the spectrometer 15allowing for passage of the species gathered from the plasma effluent 31to the spectrometer 15. The plasma plume 32 within the secondary plasmachamber 309 performs a similar function to the filters 214 a, 214 b, 214c thereby breaking down larger particles for analysis by thespectrometer 15.

FIG. 5 illustrates a method of treating and analyzing tissue. To aid inthe analysis of tissue, in step 500, a contrast agent may be addedthereto. Step 500 is optional, based on the needs of the user. Thecontrast agent may be any type of substance that can be injected,ingested or otherwise provided to the patient that has different uptakerates by malignant and healthy tissues. In step 502, the plasmaapplicator 12 is used to generate and apply the plasma plume 32 to thetissue thereby generating the plasma effluent 31. In step 504, theplasma effluent 31 is collected by the plasma analysis device 200 or the300, in particular, by the effluent-collection attachments 204 or 304.The negative pressure source 17 provides for the flow of the plasmaeffluent 31 into the effluent-collection attachments 204 or 304, whichthen filter (or otherwise process) the particles contained in the plasmaeffluent 31 prior to transporting them to the spectrometer 15.

In step 506, the spectrometer 15 analyzes the plasma effluent 31. In oneembodiment, this may be done by analyzing the plasma effluent 31 forprotein types and sizes. Protein types are indicative of types oftissue, and the analysis results may be processed by the computingdevice 19 to output the tissue type for the user. The output may beprocessed in real-time to provide the user with real-time biopsyresults, namely, continual updates regarding the type of tissue beingtreated.

Protein sizes are indicative of the efficiency of energy delivery to thetissue. More specifically, the size of the protein chains is inverselyproportional to the energy being delivered to the tissue (e.g., largeramounts of energy result in smaller protein chains). The filters 214 a,214 b, 214 c of the effluent-collection attachment 204 are used tofilter the proteins to obtain the particles of desired size foranalysis. In another embodiment, the effluent-collection attachment 304is used to break down the particles from the plasma effluent 31 to thedesired size.

In step 508, the computing device 19 processes the data from thespectrometer 15. The computing device 19 determines tissue type and/orprogression of treatment. In one embodiment, the computing device 19 maycontinually update the analysis results based on the data received fromthe spectrometer 15. This may be particularly useful in treatingcancerous tissue (e.g., skin cancer), since the computing device 19 mayindicate when majority of the cancerous tissue has been removed. Inanother embodiment, the analysis may be done after the treatment, basedon the samples collected by the filters 214 a, 214 b, 214 c. This typeof analysis is more suited for a more detailed, post-treatmentdetermination of the type of tissue.

In one embodiment, the system and method of the present disclosure maybe utilized in a Mohs procedure, which is a type of a surgical procedurefor treating skin cancer. The disclosed systems and method are suitablefor simultaneous resectioning and examination of the removed tissue,which is one of the main goals of the Mohs procedure.

Although the illustrative embodiments of the present disclosure havebeen described herein with reference to the accompanying drawings, it isto be understood that the disclosure is not limited to those preciseembodiments, and that various other changes and modifications may beeffected therein by one skilled in the art without departing from thescope or spirit of the disclosure.

1-6. (canceled)
 7. A method for treatment and analysis of tissuecomprising: generating and supplying a plasma plume to tissue through aplasma applicator to form a plasma effluent; collecting a portion of theplasma effluent through an effluent-collection attachment; analyzing theportion of the plasma effluent with a spectrometer to generate plasmaplume data; and processing the plasma plume data to determine at leastone of a type of the tissue or effectiveness of energy delivery to thetissue.
 8. A method according to claim 7, further comprising: adding acontrast agent to the tissue, wherein the contrast agent has differentuptake rates for malignant and healthy tissue.
 9. A method according toclaim 8, wherein processing the plasma plume data further includes ofdetermining an amount of malignant tissue based on a presence of thecontrast agent in the plasma plume.
 10. A method according to claim 7,wherein collecting the portion of the plasma effluent further includesfiltering the portion of the plasma effluent through a plurality offilters.
 11. A method according to claim 7, wherein collecting theportion of the plasma effluent further includes passing the portion ofthe plasma effluent through a plasma chamber.
 12. A method according toclaim 7, wherein of collecting the portion of the plasma effluentfurther includes supplying a negative pressure source to theeffluent-collection attachment to provide for a flow of the portion ofthe plasma effluent through the effluent-collection attachment.
 13. Amethod according to claim 7, wherein processing the plasma plume datafurther includes determining a ratio of malignant to normal tissue andoutputting the ratio.
 14. A method according to claim 13, furthercomprising: determining progression of malignant tissue based on theratio; and terminating generation and supply of the plasma plume basedon the determined progression.
 15. A method for treatment and analysisof tissue comprising: generating and supplying a plasma plume to tissuehaving malignant and normal cells through a plasma applicator to form aplasma effluent; collecting a portion of the plasma effluent through aneffluent-collection attachment; analyzing the portion of the plasmaeffluent with a spectrometer to generate plasma plume data; processingthe plasma plume data to determine a ratio of malignant to normaltissue; and determining progression of malignant tissue based on theratio and terminating generation and supply of the plasma plume based onthe determined progression.
 16. A method according to claim 15, furthercomprising: adding a contrast agent to the tissue, wherein the contrastagent has different uptake rates for malignant and healthy tissue.
 17. Amethod according to claim 16, wherein processing the plasma plume datafurther includes determining an amount of malignant tissue based on apresence of the contrast agent in the plasma plume.
 18. A methodaccording to claim 15, wherein collecting the portion of the plasmaeffluent further includes filtering the portion of the plasma effluentthrough a plurality of filters.
 19. A method according to claim 15,wherein collecting the portion of the plasma effluent further includespassing the portion of the plasma effluent through a plasma chamber. 20.A method according to claim 15, wherein collecting the portion of theplasma effluent further includes supplying a negative pressure source tothe effluent-collection attachment to provide for a flow of the portionof the plasma effluent through the effluent-collection attachment.